1. Field of the Invention
The invention concerns a reinforced disk spring, the reinforced disk spring of the invention comprising a conical shell of elastically deformable material having an upper, plane or convex surface, a lower concave surface, an outer bounding surface and an inner bore.
2. Description of the Prior Art
Disk springs, also termed Belleville springs after their inventor, are conical shells of rectangular or trapezoidal cross-section. In addition, they are often provided with an upper flat bearing surface adjacent to the bore and a lower flat bearing surface adjacent to the bounding surface through which the load is applied. The disk springs mostly used in mechanical engineering are of steel and other metals which, depending on the required spring characteristics, are employed individually or in groups, of which the latter can be stacked in "series" or in "parallel." These isotropic disk springs are described with particularity in the following literature:
(A) Siegfried Gross: "Berechnung und Gestaltung von Metallfedern," 3rd edition, 1960 Springer, pages 61- 79;
(B) J. O. Almen and A. Laszlo: "The Uniform-Section Disk Spring, " Transactions of the ASME, Vol. 58, 1936, pages 305- 314.
Disk springs of electrically insulating materials are required in the construction of generators and transformers. Such springs are at present made from glass-fibre-reinforced plastics (GRP) which possess a relatively good combination of stiffness and strength. Disk springs of laminated material, of rings cut from tubes, and corrugated plates are used.
A disadvantage of the presently known GRP disk springs is that their stiffness is much lower than that of steel springs. Furthermore, with these disk springs, increased stiffness cannot be achieved by stacking them, as is the case with steel springs, because the bounding surfaces between adjacent springs cannot be permanently lubricated. For this reason, the stiffness, and hence the spring constant, of a GRP disk spring is severely limited and in many cases is insufficient. Moreover, the reinforcement provided by the fibres of known disk springs is "non-directional, " i.e., the fibres offer no directed resistance against specific deformations. Instead, this reinforcement is excessive with respect to some of the forms of deformation, while it is inadequate with respect to other kinds of deformations, especially at relatively high loads. The stiffness of the spring, and hence its load capacity, therefore suffers.